The ability to efficiently connect many high-speed ports is of critical importance for large-capacity data processing. By taking advantage of the parallel nature of light, two-dimensional (2-D) optical planes can be employed to avoid the eventual electronic bottlenecks of reduced speed and increased power consumption. However, a basic problem arises in the optical-plane solution when one plane wishes to communicate simultaneously or reconfigurably with many subsequent planes. Traditional optical systems solve this problem in two ways. The first approach is for each plane to detect a data packet and then, if it is not intended for that plane, retransmit it to the next plane; see, e.g., J. W. Goodman, "Optics as an Interconnect Technology", in Optical Processing and Computing, H. H. Arsenault et al, Eds., Academic Press, Inc., New York (1989). This configuration is depicted in FIG. 1a, discussed below. The disadvantages include the possibility of an electronic high-speed bottleneck as well as the wasting of capacity, real estate, and optical hardware.
The second approach involves etching large via-hole windows in each plane's substrate such that an unobstructed and permanent optical path is created between a transmitting pixel on plane i and a detecting pixel on plane j; see, e.g., A. Dickinson et al, "Free-space optical interconnection scheme" , Applied Optics, Vol. 20, No. 14, pp. 2001-2005 (10 May 1990) and W. T. Cathey et al, "High concurrency data bus using arrays of optical emitters and detectors" Applied Optics, Vol.18, No.10, pp. 1687-1691 (15 May 1979). This configuration is depicted in FIG. 1b, also discussed below. This second approach solves the electronic bottleneck but wastes real estate and allows only a predetermined static connection between any two planes.
Thus, a need remains for efficiently coupling many high-speed optical ports from one plane to another such that reconfigurability and simultaneity can be accomplished without wasting real estate.